LIDAR system for real-time standoff detection of bio-agents is presented and preliminary experimental results are
discussed. The detection approach is based on two independent physical phenomena:
(1) laser induced fluorescence (LIF),
(2) depolarization resulting from elastic scattering on non-spherical particles.
The device includes three laser sources, two receiving telescopes, depolarization component and spectral signature
analyzing spectrograph. It was designed to provide the stand-off detection capability at ranges from 200 m up to several
kilometers. The system as a whole forms a mobile platform for vehicle or building installation. Additionally, it's
combined with a scanning mechanics and advanced software, which enable to conduct the semi-automatic monitoring of
a specified space sector.
For fluorescence excitation, 3-rd (355 nm) and 4-th (266 nm) harmonics of Nd:YAG pulsed lasers are used. They emit
short (~6 ns) pulses with the repetition rate of 20 Hz. Collecting optics for fluorescence echo detection and spectral
content analysis includes 25 mm diameter f/4 Newton telescope, Czerny Turner spectrograph and 32-channel PMT.
Depending on the grating applied, the spectral resolution from 20 nm up to 3 nm per channel can be achieved.
The system is also equipped with an eye-safe (1.5 μm) Nd:YAG OPO laser for elastic backscattering/depolarization
detection. The optical echo signal is collected by Cassegrain telescope with aperture diameter of 12.5 mm.
Depolarization detection component based on polarizing beam-splitter serves as the stand-off particle-shape analyzer,
which is very valuable in case of non-spherical bio-aerosols sensing.